Index tabs for quick identification and selection of file folders are a regular feature of almost every modern office. Typically, these tabs are located on the edges of folders which are stacked or hung, or are provided as markings on certain pages of books, notebooks, or other sheet material. In order to facilitate scanning and selection of the folders or pages, the tabs are staggered with respect to each other; for example, the tab mounted on the edge of a subsequent folder is positioned just far enough to the right of the tab mounted on the edge of the immediately preceding folder that the identifying text written on both tabs can be seen when the folders are stored next to one another.
In general, indexing tabs are manufactured in one of two ways: the tabs may be formed as protrusions of the folders or pages themselves, or the tabs may comprise separate elements which are secured to the folders or pages.
Forming index tabs as protrusions of the folders themselves is disadvantageous, since it is difficult to print identifying text on the tabs. It is impractical to insert the entire folder into a typewriter in order to type text onto the edge protrusion, and it is difficult or impossible to run the folders directly through common office printers, especially laser printers. This drawback is all the more pronounced when the tabs are to be used to mark pages of a book. As a result, the identifying text is usually either handwritten onto the tabs, or else the text is printed on separate adhesive labels which are then placed on the corresponding tabs.
U.S. Pat. No. 4,201,403 (Turner) illustrates a simple, common form of index tab, having a portion of one surface coated with adhesive, as well as a non-adhesive printing surface. In use, identifying text is printed on the printing surface. The tab is then mounted on the edge of, e.g., a page of a book, by pressing the adhesive surface against the page so that the printing surface protrudes beyond the edge. In an alternative embodiment, both of two opposite edge portions of each tab are coated with adhesive, a printing surface being defined between the adhesive portions. The tab is mounted on an edge by folding it over the edge along an intermediate score line, whereby the coated edge portions face each other and adhere to either side of the edge region of the page.
The index tabs described in U.S. Pat. No. 3,001,306 (Wilkinson) are similarly mounted by folding them over the edge of the folder or page. To improve the ability to store and print these tabs, they are initially provided on a strip-like backing sheet, which is rolled or coiled; such a coil, however, precludes printing using typically sheet-fed printers such as laser printers. Unlike the above-mentioned tabs according to Turner, the surface of an entire side of each tab according to Wilkinson is coated with adhesive, the opposite, printing side being entirely free of adhesive. In use, each tab is removed from the coiled backing strip and is folded over the edge of the sheet to which it is to be attached so that the adhesive side faces opposite sides of the sheet, and so that a central portion of the tab protrudes beyond the edge. The adhesive surface on either side of the sheet is then pressed against the sheet, thus securing the tab.
The above-mentioned tabs according to the prior art may be printed upon much more easily than tabs formed as protruding elements of an edge; however, in order to position the tabs precisely, for example in a laterally staggered relationship on the edges of a series of folders or sheets, great care must be taken when mounting them. Furthermore, once the adhesive surface of a tab comes into contact with the sheet on which it is to be mounted, it will tend to adhere to the sheet and make it difficult to align or otherwise adjust the position of the tab. This problem is particularly pronounced when using tabs according to the Wilkinson design of U.S. Pat. No. 3,001,306, since the edge of the sheet member on which a Wilkinson tab is to be mounted must be carefully aligned between two adhesive wings.
A further disadvantage of prior art indexing tabs which are suitable for machine printing is that they are supplied either as a coil, such as the Wilkinson tabs, or on some other continuous web, such as the commercially available coiled or fan-folded, pin-fed label sheets. First, providing labels on such a continuous web backing material is cumbersome both when initially feeding the web into the printer and also when removing it; this is particularly undesirable when only a few index tabs or labels need to be printed. Second, the high-quality printing devices such as laser printers most commonly found in offices normally are sheet-fed, so that they could not be used for printing index tabs or labels according to the prior art without special adaptation.
A particular disadvantage of prior art tabs, such as the Wilkinson tabs, with fold or score lines is that fold or score lines are also made in the main printing surface of the tabs. When typing or printing on such tabs, symbols which fall on the fold or score lines will be unclear and ugly.
Accordingly, one object of the present invention is to provide index tabs suitable for group printing using sheet-fed devices such as a laser printer.
A further object of the invention is to provide index tabs which facilitate proper positioning on the edge of a sheet while minimizing the risk of inadvertent, premature adhesion.